The use of indicators to measure the volume of liquid or gas in tanks or containers is well known. Such indicators are typically of the invasive type, in that they are constructed to measure the volume or level of liquid or pressure of a gas in a tank or container through the use of one or more members or devices that reside within the tank itself or that are in liquid or gas communication with the inside liquid- or gas-containing chamber of the tank. Such invasive-types of liquid or gas measuring devices can include one or more members that are also disposed outside of the tank. Invasive measuring devices are adequate for use in certain applications where the tank is either not covered or enclosed, or is covered and pressurized or not pressurized.
However, even in these types of containers the use of invasive measuring devices may not be the most suitable method for determining the volume content of the liquid or gas disposed therein. For example, the placement of an invasive measuring device within the volume of a container in certain applications may carry with it the risk of possibly contaminating the liquid or gas disposed there, e.g., when the liquid or gas is of a high purity. Further, exposing one or more element of a measuring device to the liquid or gas being measured may carry with it the risk that such exposed elements may become damaged, e.g., in the case where the liquid or gas is corrosive or the like. Additionally, the use of such an invasive measuring device also requires a breach of the container structural wall, which can introduce a source for a possible leak path of the liquid or gas from within the container. The introduction of such a leak path may not be desired in certain applications where an unintended release or the liquid or gas could present a health, safety or environmental risk.
Additionally, there are certain types of specialized liquid or gas handling containers that are pressurized for the purpose of performing a particular function. An example of this type of container is a hydraulic surge suppressor that comprises a pressurized diaphragm disposed therein for the purpose of accommodating a pressure surge or hydraulic transient in the fluid line that it is attached to. In such an example application, it is intended that the gas within the diaphragm be maintained under substantial precharge pressure for the purpose of attenuating any fluid surge within the fluid line. Because the pressure vessel comprises an elastomeric bladder disposed therein, the use of conventional invasive-types of volume measurement devices can present a challenge (due to the combined contents of a liquid volume and a gas-filled elastomeric bladder), and can interfere with the intended operation of the device. Further, because such surge suppressors are operated at elevated pressures, it is desired that the container not include any perforations or holes through the structural wall.
In addition to the above-noted issues related to measuring liquid or gas volumes in a container by invasive devices or methods, it is desired for certain liquid and gas volume measurement applications that the measuring device and/or the instrumentation used with the same be sufficiently portable to permit the unhindered measurement of a number of tanks or containers at one or more locations. In order to provide such flexibility using an invasive method of volume measurement, each tank or container being measured would have to in advance be constructed to include the invasive measurement device, which adds both to the initial cost of constructing the container and the later costs of servicing and maintaining proper operation of the measurement device.
It is, therefore, desired that a device and method for using the same be provided that is capable of obtaining an accurate measurement of liquid or gas volume within a container in a non-invasive manner. It is desired that such device be capable of providing such volume measurement in liquid or gas containers that may or may not comprise a pressurized diaphragm or other type of pressurized member therein. It is further desired that such noninvasive volume measurement device be somewhat portable so that it can be used to measure the volume in more than one liquid container in a manner that is both time and cost effective.